Vaccine Helping Frog Population Rebound

(CN) — A native California frog is fighting its way back from near extinction after scientists developed a vaccine against a disease that has killed off more than 200 species of amphibians around the world in the last 30 years. The Sierra Nevada yellow-legged frog – known for the coloring under its hind legs – lost 90 percent of its population due to the introduction of non-native trout in their habitats and a disease called chytrid fungus, which is deadly to amphibians. Once so plentiful that dozens of frogs would hop away with each step of an approaching person, their numbers began to plummet about a century ago before rebounding in the last 20 years, according to lead researcher Roland Knapp. Officials at Yosemite National Park stopped stocking non-native fish in some lakes, which helped the frog population increase sevenfold. “It’s got a long way to go to get to where it was,” Knapp told The Associated Press. “It’s certainly an important milestone.” In recent years, the chytrid fungus threatened the survival of the frogs. This prompted scientists to create a vaccine using small amounts of the fungus, allowing the frogs to develop a resistance to the disease. Developing similar vaccines, along with better management practices, could reverse the decline of amphibians elsewhere, researchers say. The promising rebound of the frog is limited to Yosemite, which makes up 13 percent of its historical habitat in the Sierra. The frog remains scarce elsewhere in the range. The yellow-legged frog is protected as a federally endangered species, and state wildlife officials consider it threatened in California.